Water reducers are special chemical products added to a concrete

Concrete

Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

 mixture before it is poured. They are from the same family of products as retarder

Retarder (chemistry)

A retarder is a chemical agent that slows down a chemical reaction. For example, retarders are used to slow the chemical hardening of plastic materials such as wallboard, concrete, and adhesives.Sugar water acts as a retarder for the curing of concrete...

s. The first class of water reducers was the lignosulfonates which has been used since the 1930s. These inexpensive products were derived from wood and paper industry, but are now advantageously replaced by other synthetic sulfonate

Sulfonate

A sulfonate is a salt or ester of a sulfonic acid. It contains the functional group R-SO2O-.- Sulfonate salts:Anions with the general formula RSO2O− are called sulfonates. They are the conjugate bases of sulfonic acids with formula RSO2OH. As sulfonic acids tend to be strong acids, the...

 and polycarboxylate, also known as superplasticizer

Superplasticizer

Superplasticizers, also known as high range water reducers, are chemicals used as admixtures where well-dispersed particle suspension are required. These polymers are used as dispersants to avoid particle aggregation, and to improve the flow characteristics of suspensions such as in concrete...

s.

Water reducers offer several advantages in their use, listed below:

• reduces the water content by 5-10%
• decreases the concrete porosity
  Porosity
  Porosity or void fraction is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0–1, or as a percentage between 0–100%...
  
  
• increases the concrete strength
  Strength of materials
  In materials science, the strength of a material is its ability to withstand an applied stress without failure. The applied stress may be tensile, compressive, or shear. Strength of materials is a subject which deals with loads, deformations and the forces acting on a material. A load applied to a...
  
   by up to 25% (as less water is required for the concrete mixture to remain workable)

• increases the workability (assuming the amount of free water remains constant)

• reduces the water permeability
  Permeability (fluid)
  Permeability in fluid mechanics and the earth sciences is a measure of the ability of a porous material to allow fluids to pass through it.- Units :...
  
   (due to less water being used)

• reduces the diffusivity
  Diffusivity
  Diffusivity can refer to:*Diffusivity of heat*Diffusivity of mass:** Molecular diffusivity ** Eddy diffusivity*Momentum diffusivity...
  
   of aggressive agents in the concrete and so improves the durability of concrete
• gives a better finish to surfaces (due to all of the above)

See also

• Plasticizer
  Plasticizer
  Plasticizers or dispersants are additives that increase the plasticity or fluidity of the material to which they are added; these include plastics, cement, concrete, wallboard, and clay. Although the same compounds are often used for both plastics and concretes the desired effects and results are...
  
  
• Superplasticizer
  Superplasticizer
  Superplasticizers, also known as high range water reducers, are chemicals used as admixtures where well-dispersed particle suspension are required. These polymers are used as dispersants to avoid particle aggregation, and to improve the flow characteristics of suspensions such as in concrete...
  
  
• Cement
  Cement
  In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
  
  
• Admixture